#include <bits/stdc++.h>
using namespace std;
 
typedef long long int ll;
 
int main() {
    int n;
    cin >> n;
 
    vector<ll> A(n);
    for (int i = 0; i < n; i++) {
        cin >> A[i];
    }
 
    ll counter = 0;
 
    unordered_map<ll, ll> mp;
 
    for (int j = 0; j < n; j++) {
     ll real = A[j]%5;
 
     ll r= 5 - real;
 
     r = r%5;
 
     counter+= mp[r];
 
     mp[A[j]%5]++;
 
 
 
    }
 cout<<counter<<endl;
    return 0;
}

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NgoyIDIgNSA1IDMgMw==

6
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